1. Technical Field
This invention relates generally to a computer-controlled device and method for determining the shape and size of a human extremity such as a foot. More particularly, the invention provides foot sizing information by illuminating the periphery of the foot with near-infrared wavelength light and capturing an image of the illuminated foot through a transparent plate.
2. Related Information
There is a need to quickly, accurately, and inexpensively capture detailed information representing the shape and size of a human extremity such as a foot or hand. One application of the invention is the determination of a person's shoe size in a shoe store or other commercial setting. Other applications may include biometric identification of humans based on hand geometry.
Conventional approaches for sizing a human foot have generally required a large number of parts and mechanical structures, many of which may require calibration. As one example, U.S. Pat. No. 5,361,133 to Brown et al. discloses a technique for measuring feet which uses both pressure sensors and infrared LEDs. The device includes two footwells each including a pressure sensitive pad and IR diode assemblies. Dozens of circuits are interconnected to receive, convert, and analyze information detected from feet placed into the device.
Another approach disclosed in U.S. Pat. No. 4,604,807 to Bock et al. uses a light source positioned above a foot to project light onto the foot, causing a shadow projection from the foot to be received on a photosensitive array. The shadow projection is used in unspecified algorithms to determine foot size information.
Yet another technique, exemplified by U.S. Pat. No. 5,025,476 to Gould et al., involves projecting a moire fringe pattern through a transparent plate onto the underside of a foot, receiving the image in a computer, and determining foot parameters by calculating distances between various points in the captured image. A special opaque light shield or "sock" is required to prevent ambient light from interfering with the measurements.
The inventors of the present invention have found that conventional approaches for sizing human feet are often inaccurate, expensive, and cumbersome, and are generally unsuitable for use in a large-scale commercial setting such as shoe stores.